Underwater archaeologist Karl Brady, co-author of Warships, U-Boats And Liners, said less than half of the 300 wrecks mapped by the State survey have been identified so far.
More than 13,000 ships have sunk in Irish waters, most within 20 miles of the coast.
The most dangerous era was during the First World War when 1,700 ships were sunk. In the Second World War, a further 800 ships were sent to the bottom of the sea, said Mr Brady.
Torpedo casualties include the SS WM Barkley, owned by Guinness's Brewery in Dublin, which was targeted by a German submarine as it was bringing a load of stout from Dublin to Liverpool in 1917. It was torpedoed east of Howth Head and sank with the loss of four lives.
The following year, the SS Polwell was sunk by a German torpedo eight kilometres north-east of Lambay Island.